Fibrous product and method thereof with thermoplastic polymeric impregnant

ABSTRACT

An improved article of manufacture and method thereof utilizing a fibrous structure of initially discrete layers, each having first and second sides. At least one side of each layer is rough and the structure has a shrinkage of no more than about 2 percent. The structure is impregnated with a thermoplastic-type polymeric material, and in the final structure there is no visible layer separation.

This is a division of application of Ser. No. 08/394,557, filed Feb. 27,1995, now U.S. Pat. No. 5,482,751, which is a continuation of Ser. No.08/004,955 filed Jan. 15, 1993 and now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to fibrous products and a methodof making same, and more particularly to an improved polishing productand method of manufacture thereof.

Products made in accordance with the present invention can be utilizedfor a number of various applications such as polishing, wicking and thelike. The present application describes the improved product and methodwith respect to a polishing product, such as utilized for glasspolishing, but it should be understood by one of ordinary skill in theart that there are a number of suitable applications for the presentinvention, including but not limited to those set forth above.

Many attempts have heretofore been made to fabricate pads for polishingand/or grinding of various and sundry shapes and materials toaccommodate for the wide variety of uses noted above, and in general,have succeeded in affording some economic and/or technical improvementin the then state of the art processes. Though such improvements haveheretofore been made, problems continue to exist for various and sundryreasons. Notably, needled natural and synthetic fibrous felts have beenproduced and utilized as polishing pads though historically suchproducts have been lacking in uniformity of density, porosity, and thelike. Furthermore, historically there have been limits to the thicknessof such needled fibrous products though attempts have been made to tackplural layers together to build up a thicker composite polishing pad.

Other attempts have been made to produce composite pads in whichdiscrete fibrous layers have been adhesively secured together. Again,the adhesive interfacial layers present a different effect in theworking of abrasives or the like across a work surface than the fibrouspad, leading to possible changes in surface characteristics. Likewise,adhesive bonds are subject to fail, leading to delamination with sameattendant results as noted above.

In recent years, following at least the advent of the poromericsynthetic leather materials the fibrous pads or substrates have beenimpregnated with porous elastomeric materials. The elastomeric materialsemployed have often been urethane based and have been variously appliedto the fibrous materials from both solvent and aqueous systems.

Currently, polishing products such as wheels, and the like, aremanufactured from non-woven substrates by die cutting to the desiredshape or by lamination with adhesive between adjacent layers of materialfollowed by cutting the substrate to the appropriate shape. Thelaminating process is more efficient from a material standpoint in thatthere is little if any wasted substrate material. In addition, thelaminating process allows products or wheels to be constructed that havea greater thickness than can be manufactured by die cutting unitarysubstrates. In the die cutting of unitary substrates, there is a greatdeal of wasted material and there are limitations of the thickness ofthe final product that can be manufactured. However, a wheel from aneedled substrate is much less susceptible to coming apart duringpolishing or grinding operations because it is of one piececonstruction.

A disadvantage of laminated polishing products such as spiral woundwheels is that in the prior art, adhesive has been required to maintainthe wheel or polishing product in a wound state. It has been found thatthe adhesive layers may act as a barrier to uniform wicking of slurriesor impregnation in a laminated product and may also pick up particles ofthe article being worked or large particles of abrasives and scratch thesurface of the article being polished or ground.

In one conventional process of manufacturing spiral wound polishingwheels, a layer of fibrous substrate material is provided with anadhesive applied to one side of the material. The material is thentightly wound and the roll is placed in an oven for a period of time toallow the adhesive to cure. The roll material is then sliced andfinished. Another known process of manufacturing a spiral woundpolishing wheel is to cast a film of resin on a sheet of silicone paper.Then a fibrous substrate material is provided and the film is laid downon one side of the substrate. The roll is wound so that the film ofadhesive is between adjacent layers of the roll. After processing,wheels are then cut from the roll. Both of these methods of forming aspiral wound wheel suffer from the disadvantages discussed above.

SUMMARY OF THE INVENTION

The present invention recognizes and addresses the foregoingdisadvantages, and others of prior art constructions and methods.

Accordingly, it is an object of the present invention to provide animproved article of manufacture.

It is another object of the present invention to provide an improvedmethod of producing an article of manufacture.

It is another object of the present invention to provide an improvedfibrous article and method of making same.

It is another object of the present invention to provide an improvedspiral wound article of manufacture and method of making same for use inpolishing and/or grinding glass and the like.

It is another object of the present invention to provide an improvedporomeric laminated article without adhesive between adjacent layers.

It is yet another object of the present invention to provide an improvedspiral wound article without adhesive between adjacent layers.

Another object of the present invention is to provide an improvedfibrous product for polishing and/or grinding of glass, soft metals,ceramics or the like which product is impregnated with a polymericcomposition that is thermoplastic in nature.

These and other objects are achieved by providing an improved article ofmanufacture comprising a fibrous structure of initially discrete layers,each layer having first and second sides. At least one side of eachlayer is rough and the structure is made from fibers or a fiber blendwhich has a shrinkage of no more than about 2 percent. The structure isimpregnated with a polymeric material characterized as thermoplastic. Ina preferred embodiment, the structure is comprised of a blend ofpre-shrunk fibers, and at least one of the first and second sides ofeach discrete layer has a roughened surface and with an opposite sidecalendered.

These and other objects are also achieved in one embodiment by providinga process of manufacturing articles including the steps of winding aplanar fibrous structure having a shrinkage of not more than about 2percent upon itself to form a spiral wound roll, one side of thestructure having a rough surface and the opposite side of the structurehaving a smooth surface. The process includes the further step ofslicing, die cutting or otherwise cutting the spiral wound roll into aplurality of individual articles, impregnating the individual articleswith a polymeric material having thermoplastic characteristics andcuring the individual articles.

Likewise, the entire roll of layered fibrous material may be impregnatedwith the thermoplastic type polymer and cured, after which the productcan be finished and used or cut into a desired shape and finished. Stillfurther, roll formation is not necessary in that the layers can be flatpressed together to achieve a coherent, structurally sound productwithout the need for adhesives, though in pressing both sides of thelayers can be rough.

These and other objects are accomplished by providing a method ofmanufacturing articles that comprises laminated strips of fibroussubstrate with a shrinkage of not more than 2 percent and at least oneside rough.

Other objects, features and aspects of the present invention arediscussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, to one of ordinary skill in the art, is set forthmore particularly in the remainder of the specification, includingreference to the accompanying figures, in which:

FIG. 1 illustrates a perspective view of a prior art laminated polishingproduct;

FIG. 2 is a cross-section of FIG. 1 taken along lines 2--2 illustratingthe adhesive between layers in a prior art polishing product;

FIG. 3 illustrates a roll of fibrous substrate in accordance with anembodiment of the present invention;

FIG. 4 is a perspective view of a product in accordance with anembodiment of the present invention;

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 4illustrating an embodiment of the present invention;

FIG. 6 is a perspective view of strips of material in accordance with anembodiment of the present invention; and

FIG. 7 is a perspective view of the strips of FIG. 6 after being pressedtogether.

Repeat use of reference characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It is to be understood by one of ordinary skill in the art that thepresentdiscussion is a description of exemplary embodiments only, and isnot intended as limiting the broader aspects of the present invention,which broader aspects are embodied in the exemplary construction.

Referring to FIGS. 1 and 2, a prior art laminated, and in this case,spiralwound type polishing product is illustrated generally at 10. Thisproduct is constructed as a wheel with an internal diameter for beingplaced on a polishing machine and a face 12 for polishing products suchas glass mirrors and the like. Referring to FIG. 2, which is across-section of FIG. 1 taken along lines 2--2, it can be seen thatwheel 10 consists of a number of discrete layers 14 of fibrous materialsuch as nonwoven polyester substrate. Separating each layer 14 is alayer of adhesive 16 utilized to bond the layers of fibrous substrate 14together. The polishing wheel of FIGS. 1 and 2 may be formed in themanner as set forth in the background of the invention above. As can beseen from FIG. 2, the fibers of the individual layers 14 are separatedby adhesive layer 16. Fibrous substrate for the production of theproduct illustrated in FIG. 1 has routinely been produced by someneedling operation followed by needling and impregnation or adhesivejoining of the layers after impregnation. The polishing productillustrated in FIG. 1 is conventionally impregnated with an elastomericmaterial such as a urethaneto form a poromeric polishing product.

Prior art wheels such as depicted in FIG. 1 have also been produced byneedling adjacent fibrous layers into a composite structure as notedabovefollowed by impregnation with a thermoplastic type polymer such asa urethane and curing. While products of this nature are generallysuccessful, the needling process adds to cost of the product andpresents certain physical size limitations as discussed hereinbefore.

Referring to FIG. 3, a roll of material 20 is illustrated in accordancewith one preferred embodiment of the present invention. A sheet offibroussubstrate 22 is wound upon itself to form roll of fibrousmaterial 20. The sheet may be of any desired length and width. The sheet22, when wound, comprises discrete layers 23 which have been produced bya conventional process. Layers 23 of sheet 22 have sides 23a and 23b andends 23c and 23d. The sheet may be wound on a core such as a corrugatedtube to providefor uniform winding. The core serves as a starting pointfor the internal diameter as well as serving as a sleeve for placementof the roll on a slicing machine. In forming roll 20, adequate tensionis imparted during the winding process to achieve a tight wind withoutelongation of sheet 22during which fibers protruding from a rough side,e.g., 23a, contact an opposite side 23b. In a most preferred embodiment,opposite side 23b is calendered. The roll may then be held together withtape or wrap to secureit for slicing and impregnation.

In another embodiment, as illustrated in FIGS. 6 and 7, slices ofsubstratefrom a roll or sheet of material such as 22 may be cut to formstrips 33 orthe like. Strips 33 have sides 33a and 33b and ends 33c and33d. The strips33 should be prepared in the manner as set forth aboveexcept both sides can be rough and located adjacent one another asillustrated. As illustrated in FIG. 7, the adjacent layers may then beheld together by clamping or the like and pressed to form a product inaccordance with the present invention. In either embodiment, once thediscrete layers are wound or pressed, impregnated and the ultimateproduct finished by microgrinding or the like, the layers becomeindistinguishable.

In accordance with the present invention, at least one side of thesubstrate should be rough so that a fiber-to-fiber proper engagementbetween each adjacent two layers or layer portions will result when thesubstrate is rolled upon itself or the strips are pressed together.

As used herein, rough is intended to mean a surface having fibersprotruding therefrom such as would be produced by skiving or the like.No particular manner of obtaining this rough or non-smooth surface isrequired. Also as used herein, the term "smooth" is intended to meanthat the fibers lay down across the surface such as would be obtained byhot calendering, hot pressing or the like. In the spiral woundembodiment, only one rough surface between adjacent layers is suitable.In the laminated strip embodiment, both adjacent surfaces may be rough.

In one embodiment, a roughened or non-smooth surface may be accomplishedbycalendering both sides of the fibrous substrate and then skiving offan appropriate thickness of the material on one side so that the fibroussubstrate will have one face or side skived (rough) and one face or sidecalendered (smooth). In fact, by such process, two sheets may beproduced,each of which has one rough surface and one smooth surface. Insuch case, the substrate would be wound upon itself or the stripslaminated so that the skived surface will be in contact with thecalendered surface when wound or laminated.

Another method of obtaining this non-smooth or rough surface is throughneedling of the non-woven substrate. This could be accomplished byneedling from one side of the substrate entirely through the substratesufficient to cause fibers to protrude from the opposite surface. Inthis needling embodiment, the side from which the needles enter thesubstrate is suitable as a smooth surface. Likewise buffing or otheroperations may be employed to achieve a roughened surface of the layer.

It is important to the present invention that the fibrous substrate havelow shrinkage, preferably no more than about 2 percent. In oneembodiment,this may be accomplished by the use of pre-shrunk fibers.

Fibrous layers or strips employed in production of substrates inaccordancewith the present invention may be produced in any suitablefashion such as by carding, conventional production of non-wovens or thelike. The fibrouscontent of the substrate should exhibit low shrinkagepreferably no more than about 2 percent, and may include fibers of onesize or a blend of fibers of different sizes. Fine deniers arepreferred, e.g., in a range offrom about one to about 10 denier and mostpreferably in a range of from about 2 to about 7 denier. Fiber types aregenerally manmade, though natural fibers such as wool and cotton may beutilized, including blends. Preferred fibers are polyester fibers thoughother manmade fibers such as polyolefins, polyamides and the like willalso work so long as the fibers will withstand a temperature of about140°-150° F. without melting or shrinkage. In addition, natural fibersor blends may be utilized such as wools or cottons. A suitable fibrouslayer according to the present invention has a fiber density of fromabout 9 to about 65 ounces per square yard and a thickness of from about150 to about 250 thousandths of an inch. A particularly suitable fibrouslayer is a blend of polyester fibers, 662/3 percent of which have adenier of 21/2 and 331/3 percent of which have a denier of 6, a densityof about 9 ounces persquare yard, and a thickness of about 100thousandths of an inch.

In the embodiment of FIGS. 3-5, once the substrate 22 is prepared withone rough surface, it is wound upon itself to form a roll of materialwith a fiber to fiber contact between the various adjacent layerportions. It is preferred that the winding be tight but not done undersuch high tension that will elongate the sheets of fibers. One exampleof a device suitable for accomplishing this type of winding isillustrated in U.S. Pat. No. 1,076,189 to Cameron and Birch, thedisclosure of which is hereby incorporated by reference.

Once the material is wound, the roll is held together by tape or thelike and may be sliced to produce a plurality of individual wheels orotherwisedie cut or the like for a particular desired shape. Theindividual wheels or shapes are then impregnated with a thermoplastictype polymer, preferably an elastomeric material. The particularimpregnant material will depend on the final use of the wheels, but ispreferably a urethane impregnant. Examples are provided below toillustrate some preferred impregnant materials.

Referring to FIGS. 4 and 5, one product in accordance with the presentinvention is illustrated at 24 with a polishing face 26 and an edge 28.Ascan be seen, no distinction can be recognized between the layers ofthe product 24 as fibers 26 extend throughout the width of the polishingproduct. A fiber-to-fiber contact between the initially discrete layersisprovided so that the discrete layers are not separated by adhesivelayers as in the prior art.

Referring to FIGS. 6 and 7, once the substrate has been prepared with atleast one rough surface such as 33b, strips 33 are then pressed togetherso that there is fiber-to-fiber contact between the various strips. Thismay be accomplished by any suitable pressing or clamping apparatus. Theresultant product 35 may then be die cut or otherwise formed to adesired shape and impregnated and finished as set forth above withregard to the embodiment of FIGS. 3-5. It should be appreciated that inall embodiments,impregnation could occur prior to cutting into thedesired shape.

The following examples are provided for a better understanding of thepresent invention. They illustrate various fiber deniers andimpregnation processes that have successfully been utilized.

EXAMPLE 1

A substrate comprised of a blend of 662/3 weight percent 21/2 and 332/3weight percent 6 denier low shrinkage polyester fibers was needledthroughto produce a fuzzy, high friction surface on one surface. Thesubstrate wasthen tightly wound upon itself to form a spiral wound rolland held together by tape. The roll was then sliced to produceindividual wheels. Amixture of the following was prepared:

    ______________________________________                                        Trisodium phosphate    0.1    percent                                         H.sub.2 O              24.9   percent                                         Polyurethane,          20.0   percent                                         polycarbonate formed from                                                     Bisphenol A, phosgene, and a                                                  linear polyester of carbonic acid                                             Nitrile latex          20.0   percent                                         Polyurethane,          30.0   percent                                         carbonic acid ethyl ester                                                     Polyaziridine crosslinking agent                                                                     1.0    percent                                         COU, a thickener manufactured by                                                                     4.0    percent                                         Synthron, Morganton, North Carolina                                           Ammonium oxalate       3.0    percent                                         ______________________________________                                    

The components were mixed thoroughly for 20 to 30 minutes using a highspeed blender. The components were added in descending order. Theindividual wheels were placed in a bath of the above mixture where thecomposition impregnated the wheels. The impregnated wheels were thendriedin a convection oven at 150° F. for 48 hours or until dry. Thewheels were then finished and processed according to desiredspecifications including turning the inner diameter, outer diameter andsanding or microgrinding both faces of the wheel. When mounted on aglass beveling machine, the wheels successfully polished the glass.

EXAMPLE 2

A non-woven fibrous product was produced and cut into wheels as setforth in Example 1. The following components were then mixed for 20 to30 minutes using a high speed blender:

    ______________________________________                                        Polyurethane,          85.0   percent                                         carbonic acid ethyl ester                                                     COU, a thickener manufactured by                                                                     4.0    percent                                         Synthron, Morganton, North Carolina                                           Polyaziridine crosslinking agent                                                                     1.0    percent                                         H.sub.2 O              10.0   percent                                         Ammonium oxalate       3.0    percent                                         ______________________________________                                    

The wheels were then impregnated, being careful not to encapsulate thewheel. The wheels were then dried in an oven at 150° F. for 48 hours oruntil completely dry and finished by turning the inside and outsidediameters and sanding the faces as appropriate. The wheels successfullypolished mirrors.

EXAMPLE 3

Layers of fibrous substrate were prepared in conventional needlingfashion from a blend of polyester fibers of 21/2 and 6 denier, 200thousandths of an inch thick. Thereafter the layers were calendered andone side was thenskived to expose fibers and produce two layers, each ofwhich was about 100thousandths of an inch thick. One layer was thenwound tightly onto a mandrel with fibers on the skived side contactingfibers on the calenderedside and the layers were held together by tape.The roll of fibrous material was then sliced to produce a wheel and thewheel was impregnated with an elastomeric having the composition as setforth in Example 1 followed by drying. The wheels were then trued andmicroground. Testing ona beveling machine demonstrated that the wheelsperformed properly.

EXAMPLE 4

Wheels comprised of a blend of 21/2 and 6 denier polyester fiber areprepared as set forth in Examples 1, 2 and 3 above. A mixture of thefollowing components were blended in descending order for 20 to 30minutesusing a high speed blender:

    ______________________________________                                        Trisodium phosphate    0.1    percent                                         H.sub.2 O              34.9   percent                                         Polyurethane,          20.0   percent                                         polycarbonate formed from                                                     Bisphenol A, phosgene, and a                                                  linear polyester of carbonic acid                                             Nitrile latex          20.0   percent                                         Polyurethane,          20.0   percent                                         carbonic acid ethyl ester                                                     Polyaziridine crosslinking agent                                                                     1.0    percent                                         COU, a thickener manufactured by                                                                     4.0    percent                                         Synthron, Morganton, North Carolina                                           Ammonium oxalate       3.0    percent                                         ______________________________________                                    

The wheels were then impregnated in this bath without encapsulating thewheel. The wheels were dried in a convection oven at 150° F. for 48hoursor until dry. The wheels were then finished as set forth in theaboveexamples, and when tested, polished glass properly.

EXAMPLE 5

Wheels comprising polyester fibers of a blend of 21/2 and 6 denier wereprepared as set forth in the above examples. The following componentswereblended in descending order for 20 to 30 minutes using a high speedblender:

    ______________________________________                                        Trisodium phosphate    0.1    percent                                         H.sub.2 O              29.9   percent                                         Polyurethane,          20.0   percent                                         polycarbonate formed from                                                     Bisphenol A, phosgene, and a                                                  linear polyester of carbonic acid                                             Nitrile latex          20.0   percent                                         Polyurethane,          15.0   percent                                         carbonic acid ethyl ester                                                     Polyaziridine crosslinking agent                                                                     1.0    percent                                         COU, a thickener manufactured by                                                                     4.0    percent                                         Synthron, Morganton, North Carolina                                           Ammonium oxalate       3.0    percent                                         ______________________________________                                    

The wheels were then impregnated by wicking in the bath withoutencapsulating the wheel. The wheels were then removed and dried in aconvection oven at 150° F. for 48 hours or until dry. The wheels werefinished and processed as set forth above. Upon testing, the wheelssuccessfully polished glass.

EXAMPLE 6

The same steps as set forth above were carried out using the followingchemical formulation blended in the same manner.

    ______________________________________                                        Trisodium phosphate    0.1    percent                                         H.sub.2 O              44.9   percent                                         Polyurethane,          20.0   percent                                         polycarbonate formed from                                                     Bisphenol A, phosgene, and a                                                  linear polyester of carbonic acid                                             Nitrile latex          20.0   percent                                         Polyurethane,          10.0   percent                                         carbonic acid ethyl ester                                                     Polyaziridine crosslinking agent                                                                     1.0    percent                                         COU, a thickener manufactured by                                                                     4.0    percent                                         Synthron, Morganton, North Carolina                                           Ammonium oxalate       3.0    percent                                         ______________________________________                                    

In the context of the present invention, the polymeric impregnant shouldassume a thermoplastic character and, as mentioned above, is preferablyanelastomer, most preferably a urethane. When looking to end use of theproduct, hardness of the product comes into play where the work piece tobe treated has non-planar surfaces. In this situation, a softerpolishing/grinding product is desired or necessary. The same is true forthe grinding/polishing of soft metals such as gold. Forgrinding/polishingother products, however, a harder impregnated fibrousarticle may be desired. Additional hardness may be obtained by selectionof the particular impregnant, or by blending of several polymers.Accordingly, polymeric materials that are thermoset in character may beincluded in small amounts so long as the overall thermoplasticity of theimpregnant remains. Likewise it has been determined that the polymericimpregnant should have a low shrinkage characteristic which isexemplified by the urethanes of the above examples. Further, thepolymeric composition can contain minor amounts of other ingredientssuch as fillers, abrasives, dyes, etc.

While product has been produced as set forth in the examples, it isbelieved that any low shrink thermoplastic polymeric impregnant may beused to impregnate the wheels, such depending on the final use of thewheels. For example, both aqueous and solvent based polymers arebelieved to be suitable for certain end uses provided such use lowshrink polymers.

These and other modifications and variations to the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting fromthe spirit and scope of the present invention, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments may beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only, and is not intended to be limitative of theinvention so further described in such appended claims.

What is claimed is:
 1. An improved article of manufacture, said articleof manufacture comprising:a fibrous structure of initially discretelayers, each said layer having first and second sides, at least one sideof each said layer having a surface with fibers protruding therefrom,said structure being comprised of preshrunk fibers having an initialshrinkage of no more than about 2 percent; and said structure beingimpregnated with a polymeric impregnant comprising a thermoplasticpolymer.
 2. An improved article of manufacture as in claim 1, whereinsaid structure is comprised of preshrunk fibers.
 3. An article ofmanufacture as set forth in claim 1 above, wherein said sides of eachdiscrete layer having fibers protruding therefrom entangle with fiberson an adjacent layer when brought together.
 4. An article of manufactureas set forth in claim 1 above, wherein said polymeric impregnant is anelastomeric material.
 5. An article of manufacture as set forth in claim4, wherein said elastomeric material is a urethane.
 6. An article ofmanufacture as set forth in claim 5 above, wherein said urethane is awater-based urethane.
 7. An article of manufacture as set forth in claim3, wherein said surface has been skived.
 8. An article of manufacture asset forth in claim 3, wherein said surface having fibers protrudingtherefrom is achieved by needling.
 9. An article of manufacture as setforth in claim 1, wherein said structure is comprised of spiral woundlayers and only one side of each layer has a surface with fibersprotruding therefrom.
 10. An article of manufacture as set forth inclaim 1, wherein said structure is comprised of laminated strips andboth sides of each layer have surfaces with fibers protruding therefrom.11. An improved article of manufacture as defined in claim 2, whereinsaid preshrunk fibers comprise polyester fibers.
 12. An improved articleof manufacture as defined in claim 1, wherein said preshrunk fiberscomprise fibers made from a material selected from the group comprisingpolyolefins, polyamides, wool, cotton, and blends thereof.
 13. Animproved article of manufacture as defined in claim 1, wherein saidpolymeric impregnant comprises a mixture of a thermoplastic polymer anda thermoset polymer.